Circulation systems are used in well tools during well drilling operations to supply drilling fluid, or mud, to a drill bit at a bottom-hole end of a drill string. Conventional circulation systems include pumping drilling fluid through a central bore of a drill string to a drill bit, for example, to assist cooling the drill bit, flush wellbore cuttings away from the bit-rock interface, and lift the drilling fluid that carries the cuttings uphole through the annulus between the drill string and walls of the wellbore. Some circulation systems employ a circulation well tool, for example, one that includes a dropped-ball-activated sleeve valve to divert fluid flow from the central bore of a drill string to the annulus of the wellbore downhole of the sleeve valve.